Endoluminal prostheses are typically used to repair, replace, or otherwise correct a diseased or damaged blood vessel. An artery or vein may be diseased in a variety of ways. The prosthesis may therefore be used to prevent or treat a wide variety of defects such as stenosis of the vessel, thrombosis, occlusion, or an aneurysm.
One type of endoluminal prosthesis used in treatment and repair of diseases in various blood vessels is a stent. A stent is a generally longitudinal tubular device which is useful to open and support various lumens in the body. For example, stents may be used in the vascular system, urogenital tract and bile duct, as well as in a variety of other applications in the body. Endovascular stents have become widely used for the treatment of stenosis, strictures, and aneurysms in various blood vessels. These devices are implanted within the vessel to open and/or reinforce collapsing or partially occluded sections of the vessel.
Stents are generally open ended and are radially expandable between a generally unexpanded insertion diameter and an expanded implantation diameter which is greater than the unexpanded insertion diameter. Stents are often flexible in configuration, which allows them to be inserted through and conform to tortuous pathways in the blood vessel. The stent is generally inserted in a radially compressed state and expanded either through a self-expanding mechanism, or through the use of balloon catheters.
A graft is another type of endoluminal prosthesis which is used to repair and replace various body vessels. Whereas a stent provides structural support to hold a damaged vessel open, a graft provides an artificial lumen through which blood may flow. Grafts are tubular devices which may be formed of a variety of materials, including textile and non-textile materials. Grafts also generally have an unexpanded insertion diameter and an expanded implantation diameter which is greater than the unexpanded diameter.
It is also known to combine a stent and a graft to form a composite endoluminal prosthesis. Such a composite medical device provides additional support for blood flow through weakened sections of a blood vessel. In endovascular applications the use of a stent/graft combination is becoming increasingly important because the combination not only effectively allows the passage of blood therethrough, but also ensures the implant will remain open.
It is also known to provide delivery systems for delivering such prostheses intraluminally. These delivery systems generally include catheters with the prosthesis removably mounted to the distal end of the catheter. Quite often a catheter, introducer sheath, or other similar retaining means, is disposed over the prosthesis to removably support the prosthesis on the catheter. Once the prosthesis is situated in the target site in the lumen, the catheter is removed from the prosthesis.
In order to activate the prosthesis to its expanded implantation diameter, however, it is usually required to pull the sheath or retaining means away from the prosthesis to allow the expansion. The catheter typically retains and delivers the prostheses in a radially contracted state in its unexpanded insertion diameter, and removal of the catheter sheath allows expansion to the expanded implantation diameter.
Delivery and removal of the catheter sheath, however, to implant and/or activate the prosthesis presents several problems. First, catheter movement can disturb or move the introducer sheath at the wound site where the catheter is inserted into the vessel, thereby resulting in premature deployment of the prosthesis. Secondly, in tortuous anatomy, the added friction caused by rubbing the outer catheter against the vessel can make delivery and deployment of the prosthesis difficult. The translation of control movements from the proximal to the distal end of the catheter is imprecise, jerky and in some instances impossible due to the increased friction caused by tortuosity. Thirdly, delivery of the sheathed prosthesis can create trauma to the endothelium over the entire length of the catheter.
It is therefore desirous to provide an endoluminal prosthetic delivery system which delivers and activates an endoluminal prosthesis to its expanded implantation diameter without requiring removal of the catheter sheath in order to expand the prosthesis.